1. Field of the Invention
This invention relates to the mounting of ganged electrical devices into switchboxes, more specifically, it relates to a frame that facilitates such mounting.
2. Description of the Related Art
The wall switches, dimmers, and other electrical devices that are commonly installed in residences and other types of buildings are generally mounted in switchboxes (sometimes called "wallboxes" or "outlet boxes") that are located inside the walls (i.e., behind the wallboard and between the studs). The switchboxes provide the space within which the device is electrically connected to the building wiring that carries power from a central electrical panel. Switchboxes come in a standard size that accommodates a single device and that has removable side panels. These boxes can be joined together, with side panels removed, to accommodate several devices mounted ("ganged") side-by-side. Alternatively, ready-made switchboxes are available to accommodate 2, 3, 4, or more devices. Typically, an electrical device, after being mounted in a switchbox, is covered by a faceplate, which covers the opening in the wall while permitting access to the actuator (e.g., toggle switch) for the device. When more than one device is ganged in a "multigang" switchbox, a single multigang faceplate--having the appropriate access openings appropriately spaced--can cover all the devices.
Standardization plays a key role in facilitating the installation of electrical devices into switchboxes. Switchboxes generally have tapped mounting holes positioned to line up with vertically-spaced holes in the support plates (or "yokes") of the electrical devices. Generally, the yokes also have vertically-spaced tapped mounting holes positioned to line up with holes in the faceplates. Thus, one manufacturer's faceplate readily mounts onto the yoke of a second manufacturer's device, which is installed into a third manufacturer's switchbox.
An attractive appearance is provided when a faceplate surface is unbroken by a screw head; i.e., when the faceplate snaps onto the yoke, or other part, of the electrical device. The snap-on feature depends on the mating elements of the device and faceplate being aligned within rather close tolerances. Unless the elements are aligned in both a lateral (side-to-side) and "in-and-out" (i.e., normal to the wall) direction, it will be impossible to achieve a tight snap fit. When a multigang plate is to snap onto a series of ganged devices, the alignment problem is magnified. If the wall into which a group of devices is mounted is uneven or if certain errors (discussed below) were made in mounting a multigang switchbox into the wall, it may become very difficult or impossible to engage all the snap-on elements on the back-side of the multigang faceplate with the corresponding elements on the devices. If touch switches are among the multigang devices, the in-and-out spacing constraint is particularly severe, since the switch actuator must neither be "bottomed out," in constant close contact with the internal pushbutton mechanism, nor spaced too far from the mechanism to permit the switch to be operated.
Some multigang switchboxes do not have tapped mounting holes to line up with mounting holes in the yokes of all the electrical devices that the switchbox is designed to accommodate. Instead, these boxes have mounting holes only at two ends, and frames have been designed to provide the additional mounting holes. These frames have holes that are positioned to line up with the mounting holes at each end of the switchbox and, in addition, they provide mounting holes positioned to line up with holes in the yokes of a series of side-by-side devices. Among the sources for these frames is Graybar Electric Co., of Clayton, Mo.
An arrangement designed to facilitate multigang mounting of switches was disclosed in U.S. Pat. No. 2,889,437, issued June 2, 1959, to Christensen. The switches disclosed by Christensen are mounted on yokes that have an "upset" portion that overlaps a portion of the yoke of an adjoining switch and, at the same time, helps to align and locate the switches.
When the surface upon which an electrical device is to be mounted is a ceiling, rather than a wall, the problems caused by an improperly prepared surface has been addressed in the context of mounting light fixtures, particularly recessed lighting. These fixtures are typically mounted within annular "trim rings" that surround the opening that is cut in the ceiling to accommodate the fixture. When the ceiling opening is cut too large, an "oversize" trim ring is used. The oversized ring has the same inside (cut-out) diameter, to accommodate the fixture, but has a larger outside diameter, to conceal the oversized ceiling opening.